Mirror Mirror
by rockandcandy
Summary: Queen of the Vampires, heir to the Nightosphere, frontwoman of the Scream Queens. Marceline Abadeer's got it all... except for a friend who really, truly understands her. But one day Marceline discovers a cavern full of cursed mirrors, and meets Marshall Lee, a boy from an alternate dimension. He understands her, comforts her, and the two become almost inseparable until one day...
1. Prologue

Mirror, Mirror

Prologue

* * *

AN: So if you haven't guessed it yet, the mirror cavern is the one from the episode Gotcha! with LSP. If you haven't seen it yet, you should definitely watch it before you read this fic. (Or at least read the episode synopsis on the Adventure Time wiki...hehe.) Because if you don't have some background knowledge about the mirror cavern, this story isn't going to make much sense. So yeah...not much more to say...on with the story then!

* * *

"Go _away_, Dad!_ I hate you_!"

Marceline shoved her father back into a bug-milk drenched Nirvana poster hanging on the wall, and screamed the incantation to send him back into the Nightosphere.

"But Marceline! You are the heir to the Ni-"

The portal sucked her father away, his words drowned out by the howls and shrieks coming from the Nightosphere. Marceline swiped viciously at her eyes with the sleeve of her sweater, the wool coming away damp with tears. She hissed in frustration, tearing the ruined poster off the wall and throwing it into the trash.

"Why doesn't he ever understand me?! Would it _kill_ him to care about his daughter for once?"

Marceline continued to vent about her father, storming around her house and causing poor Schwable to hide quivering under the rock-hard couch. Several hours later, she still hadn't calmed down, much to the zombie dog's dismay. She had forgotten to feed him all day, and he whined in protest when she threw dessicated grey strawberries into his food bowl for dinner. The whine snapped Marceline out of her ranting, and she sighed as she knelt down to pet Schwable.

"Sorry boy, I've been a real wad today, haven't I?"

Schwable barked in agreement, pointedly looking at his food bowl.

"Ugh. I know. I'm being a horrible owner. And it's all because my dad came! That dingus ruined my day! He's just so _selfish_ and_ insensitive _and-!"

Marceline stood up and started pacing her living room again, prompting Schwable to shrink back and whine in dismay. Marceline let out a little sigh and threw her arms in the air.

"It's going to take me a while to chill. And obviously, I'm freaking you out, Schwabs. I'm...just gonna go out for a while. Cool down my head. You can take care of yourself, right boy?"

And with that, Marceline grabbed her axe bass, laced up her boots, and flew out into the night, leaving a neglected zombie dog in her wake.

* * *

Marceline flew with no direction in mind, strumming on her bass as she floated on her back. She'd been out for hours now, and the nightlife was in full swing. The owls were hooting, the wolves were howling, and the lake was...moaning?

Marceline stopped playing, and turned so that she was floating upright, over an ominous looking lake filled with ghoullish faces. "What...?"

She took a closer look at the lake, and the island in its middle. Intrigued, Marceline floated towards the blueish cave on the island, the faces in the water shrieking in protest as she passed above their reach. For a split second, Marceline's face morphed into that of a demon, baring its fangs at the faces in the lake. "Cut it out, you guys. Don't make me go in there."

Suddenly, the lake was silent.

Marceline reached the cave and peeked into the entrance. "Whoa."

"Whoa-oa-a." Marcy's voice echoed back to her.

"Hey!"

"Hey-ey-y!"

Marceline floated into the cave hesitantly, and touched down on the smooth stone floor. Pulling her axe bass down from her shoulder, Marcy strummed a few experimental chords. "Wow!"

"Wow-ow-w!"

"These acoustics are math!"

"Math-ath-th!"

Marcy smiled to herself, anticipating the rad jam session she was about to have, and walked deeper into the cave, stopping in surprise when she neared a shimmering, waterlike portal. "What is this..?"

"This-is-s..."

She stuck her hand experimentally into the portal, gasping a little as the cool, gel-like substance slid past her skin as her hand passed through the portal. Marceline pulled her hand back, and poked her head into the portal, sighing contentedly as her face slid through. As soon as her head was on the other side, Marceline gasped; she was looking into a gaping cavern, with walls covered with hundreds of natural mirrors. Marcy brought her intire body through the portal, left hand grasping the neck of her bass. In all of her one thousand and nine years living in Ooo, Marceline had never seen a cave like this. It was huge, it was majestic, and it was one heck of a good place to rock out on her bass. Marceline grinned, daddy issues forgotten for the moment, and commenced her rocking out.

She didn't notice that the portal she had come through had solidified into a stone wall, or that there was a pair of crimson demon eyes watching her every move.

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A/N: Tbh, I had like the first few paragraphs typed like a year ago, and I just dug this out recently. It was originally going to be a oneshot, but I decided to expand on it, coz I'm just cool like that. Not my best work, since my creative writing skills have been rusting in the back of my brain for a while. So sorry if I have some creative tetanus for a while, but I promise you I will improve. If you'd like to speed up the recovery process, you could always leave a review to let me know how bad off I am, and what I can improve on. Anyways, you can expect longer chapters in the future, this one's pretty short, since I believe in short prologues. So yeah, that's about it. Bye.


	2. Chapter 1

**Mirror, Mirror**

Chapter 1

Word Count: 2,288

AN: Hey guys! Jfc, it has been a literal half year since I've updated, I am so sorry. I really wish that I could promise more chapters sooner, but my life has been really hectic and the best I'll be able to promise is maybe a chapter a month? Again, I'm really sorry, and please believe me when I say I am trying my best to get a decent chapter out as soon as possible. Thanks much to _**hahaveryfunnyshutup,**_ _**nuclearbreakup**_, and a _**guest**_ for reviewing, as well as everyone who followed or favourited.

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On a rippling green plain, there stands a solitary tree with sprawling roots and a verdant green canopy that has born witness to the rise and fall of civilizations.

Built into the tree by a long-dead architect is a ramshackle house that has withstood the test of time, and is currently home to two young adventurers.

Lying forgotten in the recesses of the basement is a tape player, battered and broken and covered in dust, jammed shut and unable to play.

Loaded in the decrepit tape player is an old black cassette, miraculously unscathed by the ravages of time and still in working condition, a stack of its sisters sitting in a pile on the floor, many much worse for wear.

Peeling off the loaded cassette is an old masking tape label, a fading title carved into the surface in blue ink; intended to last for eternity but now rendered illegible save for a few words and letters...

* * *

The harsh chords of a fast-paced, erratic song ricocheted off the mirrored walls of the cavern, new notes continuously filling the silences left behind as the older notes died away. The entire cavern thrummed with music, the heavy bass lines reaching crevices of the cave that had lied undisturbed for years. A girl with jet black hair cascading down her back and a curiously shaped bass guitar held in her hands was the source of the music, and as her playing got louder her mouth opened and her crooning voice filled the cavern.

_"...All the truth unwinding, scraping away at my mind. Please stop asking me to describe..."_

Something stirred deep in the cold stone walls of the cavern, an ethereal being that had not been conscious for a long, long, while...

_"...For one moment, I wish you'd hold your stage, with no feelings at all. Open-minded, I'm sure I used to be so free..."_

The singing ceased and the girl bent over the neck of her guitar, fingers flying as she played a haunting riff. Roused by the music, something had awoken in the cavern, something dark and foreboding. Outside the cavern, birds flew away in a frenzy of caws, animals for miles around bounded away to the safety of their homes, sensing that something was not right.

_"...Self expressed, exhausting for all, to see and to be what you want and what you need..."_

Unbeknownst the the girl, the mirrors darkened and lost their reflective quality, and a pair of crimson eyes opened for the first time in a century. By now, the song had begun to reach a close, and the girl's voice had taken on a tone of anguish, eyes glistening with pain and assuming the look of one who had witnessed death and other unspeakable horrors, eyes that were haunted by nightmares as soon as they fluttered close in sleep. Eyes like those, eyes that begged for release from hundreds of years of painful memories had no place on a girl who appeared no older than nineteen.

_"...Wash me away, clean your body of me. Erase all the memories; they will only bring us pain. And I've seen all I'll ever need."_

The girl sang the last lines of the song in a soft, melodic falsetto, fingers ghosting over the strings of her bass. And as the last of the music echoed into nothingness, she bowed her head and closed her eyes, thoroughly drained from the performance. She was torn from her reverie, though, when a new sound resonated through the silent cavern. A slow, mocking clap seemed to come from everywhere and nowhere at once and the girl's head snapped up, eyes narrowed and knees bent, hands tightening around the neck of her bass as if she planned to use it as a weapon.

"Who's there?!"

The clapping was replaced by a deep throaty chuckle, and two glowing red eyes materialised in the mirrored wall in front of the girl.

"I could be asking the same thing."

A baritone voice sounded through the cavern, seemingly coming from everywhere and nowhere at the same time.

"Ugh...Show yourself, whoever you are!"

The voice laughed, "It's less a matter of who and more a matter of what."

The girl growled, her facial features twisting into something monstrous and bat-like and betraying her guise of a simple humanoid girl.

"Who. Are. You?"

"Oh, looky here. Baby's throwing a fit."

The voice laughed again, the red eyes in the mirror twinkling with a dark mirth, but cut off abruptly as the girl swung her bass into the mirror, effectively shattering it and leaving a slate black wall where the mirror used to be. If one took a closer look at the bass at this point, they would notice that the instrument she was holding was in fact an actual battle axe, fashioned into a bass guitar. When the voice spoke again, it was tinged with pain, and all traces of humour were gone.

"I suggest that you do not do that again, Marceline."

The girl was visibly taken aback, and her eyes narrowed in suspicion, glaring at thin air. "How do you know my name?"

At this point, the red eyes had reappeared in another mirror, and were currently glaring at the girl. "I know a lot of things, and I know that it'd be best if you left this cavern. Now."

The portal that the girl had come through reappeared, a thick blue gel-like substance that wavered and shone with an ethereal light. The girl however, was still firmly planted in her spot, face returned to its normal expression; one hand on her hip and her bass in the other. "I'm not leaving until you show yourself, and I'm not afraid to smash another mirror if I have to."

The voice sighed, exasperated. "I'm not showing myself, and that's final. You're just wasting your time."

The girl grinned wickedly. "Don't worry. I have all the time in the world; I can literally wait forever. So just take your time."

The voice didn't reply and the cavern was silent, but the girl could've sworn she heard a groan. So she smiled to herself and started to drift lazily around the cavern, fingers easily strumming the opening riff to a new song. She wasn't planning to leave anytime soon.

* * *

"_-Chickity china the chinese chicken, you have a drumstick and your brain stops tickin'-"_

"You know..."

The girl had been in the middle of playing quite an annoying song, knowing full well that the mystery voice had been forced to listen. She stopped playing at the sound of the voice, cackling inwardly at finally getting it to speak up again.

"Most people would be scared out of their minds right now, not playing one of the worst pre-Mushroom War songs even conceived."

The girl smirked. "Well, I'm obviously not "most people"."

"Well...everyone would've jumped at the chance to leave this place. The portal did disappear when you stumbled in."

The girl's smirk grew, revealing glistening fangs. "Then I guess you need to reevaluate your definition of "everybody"."

The cavern was silent for a few moments, the voice's annoyance palpable. When it spoke again, it was with a somewhat frustrated tone. "I guess, what I'm trying to say, is that you're different."

The girl rolled her eyes, losing interest, and her smirk was replaced with a concentrated frown as she experimented with a complicated solo from a random song. "No way, really? I totally couldn't tell."

The voice sighed, and tried again. "What I'm saying is... you're different. And you- your difference- it really interests me."

The girl's fingers died against the strings of her bass, cutting off all sound. Her eyes widened, and she burst out in laughter, cutting off the voice's affronted complaints as her laughs reverberated off the cavern walls and drowned out all other sounds. "What...what the heck? What are you even implying?"

If the voice had a face, it would have been colored scarlet from blushing. The red eyes in the mirror no longer seemed threatening, and appeared more mortified than anything. "Sh-shut up!"

The shimmering portal vanished, and the cavern seemed to darken. The girl let out a stifled noise, trying to sigh but not quite finished laughing. "Someone seems to have a flair for the dramatic."

"Hey! I'm trying to seem threatening!"

"Well, you obviously need a lot of work, then."

The girl bickered with the voice playfully, their animosity forgotten. The voice's original, threatening facade melted away and the girl dropped her defensive attitude. In time, she ended up leaning against one of the mirrored walls, her laughs mingling in the air with the voice's deep chuckles. She hugged her sides, a stitch developing from laughing so hard, and tilted her head back so that the top of her head would be against the wall and she would be looking up at the ceiling of the cavern. Except, that didn't happen.

She tilted her head back, yes, but instead of solidly pressing against the glasslike surface of the wall, the top of her head slid ever-so-slightly into the mirror. The girl's eyes widened, and she tensed up. This was a trap.

She tried to pull her head out of the mirror, to no avail. The mirror was like quicksand, and she felt her head being inexplicably pulled in. A pair of ice cold arms pushed through the wall, encircling her waist and pulling her even deeper into the mirror. At this point, almost her entire head had been pulled into the mirror, and her back was arching painfully. The arms were pulling her in faster now, and for the first time in a century, the girl was afraid for her life. "Fuck-!"

The word came out garbled and indistinguishable; her mouth had been filled with the viscous substance that the mirror wall had turned into. It was acrid and slid down her throat, she gagged and spit, but only more of the substance filled her mouth. It felt like she was drowning in honey, and she started to feel violently sick as her vampiric immune system reacted to the non-red, non-blood substance entering her body.

There wasn't much time left.

She was now shoulder deep in the mirror, and soon her arms would be immobolised as well. She groped blindly with her hands, grasping nothing but sandy dirt and small pebbles, nothing that would help her escape.

Her spine had reached its limit and she twisted involuntarily, leg lashing out, kicking something hard, and driving her body even deeper into the mirror. The owner of the arms seemed surprised by the sudden push, and loosened their grip on her waist for a split second. That split second meant everything.

Summoning all her energy, the girl lunged, sliding out of the mirror by a fraction of an inch, straining to reach the object she had kicked moments before. Her fingers scrabbled desperately, brushing something cool and metal, a single, pure note ringing out in the cavern.

Her axe bass.

With another lunge, her fingers closed around the neck of her bass. The hands had regained their grip on her now, and were pulling her into the mirror faster than ever. Using both hands, she swung the bass up and over her head, praying to Glob that her idea would work, and it did.

For some strange, unknown reason, instead of sinking into the mirror, the axe bass struck it and rebounded off. The force was so strong that it tore the instrument out of the girl's hand, launching it high in the air and it skittered out of her reach on the other side of the cavern. If the girl had been able to see the mirror she was getting pulled into, she would've seen spiderweb cracks spreading from where she hit the mirror. The cracks quickly consumed the mirror, reaching every corner of the glass. From the exact point where the axe had hit the mirror, a single shard fell, falling though the air and liquefying, landing on the girl's sternum with a soft 'plip'. The hands stopped pulling.

Then came the rest of the mirror. Shards fell, first one by one, then rapidly in groups. They rained on the cavern floor, sending up small plumes of dust where they landed, and leaving a shimmering stain when they were absorbed into the dirt.

Suddenly, the girl could see again, and her head no longer felt like it was slowly being compressed. She jerked her head forward, landing roughly on her knees and retching. Her usually long, flowing hair lay flat against her head, sodden and shimmering with the liquefied mirror. She vomited the silvery liquid, coughing and gasping in between retches. The last of the liquid she threw up was a silvery pink, tainted with the red from her previous meal. The girl was completely and utterly drained. She wiped her mouth, the back of her hand coming away glistening, and made to stand up when she heard a rustling behind her. The girl turned around.

Instead of just a dark wall, there was a small alcove where the mirror had been. And standing in the alcove, clad in clothing almost identical to her's, was a boy who could be her twin. They stared at each other, daring the other to break eye contact, and she was just about to turn away when the boy looked down and coughed awkwardly.

"Well, um, I suppose I owe you an introduction. My name is Marshall Lee, and I'm the creature that lives in these mirrors. It's, um, nice to meet you…?"

"Well, Marshall Lee, I suggest that you give me one reason not to kill you right now."

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A/N: And that's chapter one! Once again, I am so sorry that this took so long, I'll try to crank out a new one as fast as I can and possibly a oneshot as well. D: I literally worked my butt of to finish this, today. Where I live it's currently half past two in the morning and I still have an essay I need to write for English. I really hope that you enjoyed this chapter, I felt like it was a bit funky at times, and the ending is absolute crap. Anyways, thank you for reading this far! Please read and review, love you guys! xx

Song creds:

Citizen Erased- Muse

One Week- Barenaked Ladies

**ALSO: I AM LOOKING FOR A BETA IF YOU WOULD LIKE TO HELP MY HORRIBLE WRITING JUST CONTACT ME BY PM, KIK, OR EMAIL (CONTACT INFO IN PROFILE) THANKS! ILY! xx**


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